Filament wound vessels and methods for forming same



April 2, 1963 R. E. YOUNG 3,083,864

FILAMENT WOUND VESSELS AND smons FOR FORMING SAME Original Filed Nov. 26, 1957 f 2 Sheet'sSheet 1 I 10 25 9 1o 2\ 3 e I2 /AME: l2

RICHARD E. YOUNG INVENTOR.

BY W W AGENT R. E. YOUNG April 2, 1963 FILAMENT WOUND VESSELS AND METHODS FOR FORMING SAME 2 Sheets-Sheet 2 Original Filed Nov. 26, 1957 FIG. 8

FIG; 9

MM. M 1

RICHARD E'. YOUNG INVENTOR.

BY 521M141;

AGENT FIG. IO

United States Patent Office 3,083,864 Patented Apr. 2, 1963 3,@83,864 FILAMENT WGUND Will-EELS AND METHGDS F6 3. FQRMHNG SAME Richard E. Young, Rocky Hill, NJL, assignor, byniesne assignments, to Hercules Powder Qompany, Wilmington, Del a corporation of Delaware riginal application Nov. 2a, 1957, Ser. No. (599,677, now Patent No. 3,047,191, dated luly 31, 1962. Divided and this applicatien An". 11, 196i Ser. No. %,818 6 tClaims. (Qt. 229-53) This invention relates to filament wound vessels and methods for forming the same and is particularly concerned with such vessels including integral ends and having uniform strength throughout. Though the invention will principally be described as embodied in pressure vessels of iigid construction, it is to be noted that the teachings are also applicable to resilient walled vessels. Illustrations of the latter are aircraft tires and the roller type members employed for supporting vehicles such as those commonly known as marsh buggies.

In my copending application Serial No. 374,600, filed August 17, 1953, for Filament Wound Hollow Elements and Methods for Making Same, now Patent No. 2,843,- 153, granted July 15, 1958, I have disclosed and claimed filament wound hollow elements and methods for making the same. That application is concerned with the formation of open ended elements such as pipes and conduits. It does, however, disclose the basic helical filament winding pattern generally of the type embodied in the instant invention.

There is presently a very considerable demand for pressure vessels for containing fluids under relatively high pressure of a high strength to weight ratio and of high resistance against deterioration from all sources. The formation of vessels by the intermeshed helical winding of high strength filament material with a suitable resin binder lends itself admirably to the solution of this problem. For proper effectiveness, however, such vessels need to have uniform strength throughout, or, more specifically, uniform resistance to the action of internal pressure, regardless of the direction of application thereof. How to accomplish this has not heretofore been determined while embracing all of the required desiderata. Among this desiderata is the provision of vessels of a variety of sizes and shapes while maintaining their strength uniform throughout. Another is the provision of a polar plug fitting of minimum size for the ends of the vessel. Another is the ability of the vessel .to enclose a maximum volume while keeping the vessel size down to a minimum. Another has been to provide a simple and effective method for the forming of such vessels.

Still another is to provide for the generation of the proper end shape to withstand external axial end loads in combination with resistance to internal pressure.

It is, accordingly, an object of the invention to pro vide filament wound pressure vessels with integral ends formed for uniform fiber stress while yielding maximum strength to Weight ratio.

Another object is to provide such vessels accommodating polar plugs, or end fittings of minimum size.

Still another object is to provide such vessels with end shapes of high strength and of maximum internal volume.

Still another object is to provide for the formation of such vessels with end shapes capable of withstanding axial external end loads as Well as internal pressure.

A further object is to provide methods for the formation of such vessels in simple and economical manner.

A still further object is to provide such methods which can be carried out by simple equipment simultaneously depositing the various windings required.

Further and more detailed objects will in part be obvious and in part be pointed out as the description of the invention taken in conjunction with the accompanyin-g drawings proceeds:

In the drawings, wherein reference symbols refer to like parts wherever they occur:

FIG. 1 is a side elevation of a vessel in accordance with the invention;

FIG. 2 is an end elevation thereof;

FIG. 3 is a front elevation of a helical circuit winding on which the construction of the vessel is based showing the same as applied to a suitable mandrel;

FIG. 4 is a top plan view of the same;

FIG. 5 is a perspective view of one illustrative form of end fitting;

FIG. 6 is a section thereof taken on line 66 of FIG. :5;

FIG. 7 is a fragmentary radial section of a portion of a vessel in accordance with the invention taken through :one end and a portion of a joining body;

FIG. 8 is a fragmentary side elevation of a vessel in accordance with another embodiment of the invention;

FIG. 9 is an end elevation of FIG. 8; and

FIG. 10 is a side elevation of a vessel in accordance with still another embodiment of the invention wherein the cylindrical body is omitted, and the vessel is made up of a pair of substantially identical ovaloid end formations and wherein the end elevation thereof is substan tially identical to that depicted in FIG. 9.

The vessel of the invention can generally be con sidered as being formed of windings of fibrous material in conjunction with sufiicient settable binder to bind together the fibers of each layer as Well as those of various superposed layers of windings and to fill any interstices that may exist between any of those windings or layers. Thus the structure is primarily one of fibrous material with the quantity of settable binder being kept to a minimum, rather than a structure involving merely the reinforcement of a resinous body by the use of fibers. Therein lies the strength of the vessel with minimum weight and maximum resistance to deterioration.

As regards the fibers, glass is the presently preferred material for them when the structure is to be a rigid one. The invention is not, however, so limited, as other fibrous materials having preferable characteristics for any particular use may be employed in place of glass. For a flexible construction, flexible or rubber like materials are needed.

As regards the settable binder, though the epoxy resins are the presently preferred material, again, this is by way of illustration and not limitation. The selection of the particular resin or plastic depends on such things as the desired characteristics, the price and workability. Again, a flexible resin is needed for a flexible construction.

With respect to terminology, though the vessel will be generally referred to as formed of filament wound material that is by no means limiting to filamentary mate rial as commonly envisaged. Elements in accordance with the invention are considered as being filamentary whether of the commonly considered circular cross-sectional form or of a flat ribbon like formation. in this flat formation they also may fall into the category of what normally may be considered as a band. As contemplated in the application, however, bands, besides being individual elements of ribbon like form, may be composed of elements formed of a plurality of filaments laid side by side. Thus the windings forming the principal structure of the vessel of the invention may be of anything from individual filaments of fibrous material in their commonly accepted circular cross sectional form, to bands QID of iibbon like form, whether such bands be single integral members or be made up of a plurality of filaments.

For illustrative purposes, the vessel of the invention is shown as being formed with a cylindrical body 1 and ovaldid ends 2 and 3. In certain instances, however, as pointed *outhereinafter, the cylinder body may be omitted, with the vessel being made up of what would otherwise be considered as a pair of ovaloid ends. These ends are identical, so only one need -be described. The ends are each equipped with an endfitt'ing 4 providing a suitably sized opening '5 therethro'ugh. k The provision of ovalo'id "ends and the formation of the same by the portions of the windings resulting from the reversing of the basic helical winding for the body of the cylinder enables a vessel to be formed or unifor m strength throughout, so long as the proper ova'loid formation of the ends is maintained and providing that is properly related to the diameter of the body. This formation, or shape, of the ends results from a computing method and device used for the determination of the proper mandrel shape. Such method and device are described and claimed in my oo pending application entitled, Device and Method for Determining the End Pattern of Filament Wound Pressure Vessels, Serial No. 699,078, filed November 26, '1957, now Patent No. 3,005,256. As set forth in said application, it has been discovered that the contour of ovaloid ends for a vessel of the type under consideration can be determined so as to provide uniform strength of the end throughout its curvature, or, in other words, to form the wound structure of the ends so as to be in complete balance. To do this, the tension load in each filament must beconstant for every location in the end structure though the stress due to internal pressure will vary in relation to the curvature at the end.

As far as the ends are-concerned, a-complete end shaped integrally with a helically wound cylindrical body may be generatedfrom asingle system of constant helix angle. The angle of thishelix, illustrated" by the winding 6 in FIGS. -14, must normally be small, since the end fitting 4 is normally small. When, however, a mandrel, such as 7-, illustrated in dot-dash lines in FIGS. 3 and 4, is formed with ends '8 contoured as shown in those figures, by following the principles set out in my aforesaid application entitled, Device and Method for Determining the 'End Patterns of Filament Wound Pressure Vessels, the end formations, resulting from the helical winding alone, have the uniform strength desired. Furthermore, the joining of the end formations, 2 and 3, to the body portion 9 is also correct, so "long as the curvature of the mandrel 8 and consequently of the vessel ends wound thereon comes tangent to the cylinder of the body portion 8 where the ends and body join at 10, or in the case of using the end formations, 2 and 3, only, where the ends abut at 10.

The fact that the helix angle is small, leaves a strength deficiency in the girth direction of the cylindrical portion of the vessel. This, however, may be readily corrected for by the addition of circular windings, or windings at only a small helix angle with respect to a plane extending radially of the axis of the cylinder. These windings hereinaft er referred to as girth windings are preferably interspersed between the layers formed by the helical windings and are of the number calculated to make up for the girth strength deficiency for the particular vessel design.

The first step in the forming of the vessel of the invention is, of coursefth provide a suitable mandrel on which to apply the winding. This mandrel, shaped in accordance with the foregoing principles, is normally made of disposable material so that it can be removed through the end fittings once the vessel is completed. In some instances, however, it may be made of material intended to remain within the vessel as a liner therefor. In either event, the end fittings 4 are positioned on the mandrel at the ends of the vessel axis before the winding starts, since the helical windings are applied over the flanges of the end fittings.

The upper surface 12 of the end fitting flange 13 need not be contoured in continuation of the mandrel end surface 8. It is sufiicient if the surface 12 is that of a flat cone which comes tangent to the surface 8 at the point 14 where the surfaces meet.

In commencing the application of the windings to the mandrel 11, the upper surface 12 of the end fitting is primed with a resin so that the material of the winding will adhere thereto. Then, assuming that the winding is commenced adjacent the position as shown at 15 in FIG. 3, it is applied by moving the applying carriage to the right as the mandrel is turned until the winding overlies the surface 12 of the end fitting at the position 16 and tangent to the neck 5 of that fitting. Then the travel of the carriage is reversed and the winding '6, still at the helix angle 17 with respect to the axis 1'8 of the mandrel, travels across the far side of the mandrel, across the conical surface 12 of the end fitting at the other end 2 of the mandrel, again tangent to the neck 5 "of that fitting, and, after crossing its outgoing portion at the position 19, as shown in FIG. 4, returns to a position adjacent the starting point. By suitably relating the speed of the applying head to that of the mandrel, however, the helix when it returns to the starting point, does so at a position where it lies alongside of its starting portion. Thus, when a complete circuit has been made, as indicated by the points 15 and 2t lying alongside of each other, the helical winding has made one complete circuit and is ready to lay down the next circuit from a position lying alongside of the commencement of the first circuit. This next circuit, as in case of the first one and all subsequent ones, provides again for the Winding passing across the flange ll2 of the end fitting d tangent to the outside .of the cylindrical neck 5 thereof.

As the winding continues with one circuit after another being laid down alongside of the previous one, the whole of the mandrel is eventually covered with a complete layer 'of the material being wound. Along with the fibrous material of the winding, whether in filament or band form, the controlled quantity of suitable set-table resin material is applied as more fully set forth in applicant s co-pending application, Serial No. 374,600 above feferred to.

' Applications of girth windings such as 25 to the cylindrica'l b'ody portion of the vessel are dependent upon the girth strength requirements of the particular vessel. This is also related to the shape and size of the vessel and, accordingly, to the helical winding 6, for obviously a cylindrical wall formed of windings such as 6 at a small helix angle with respect to the axis of the vessel will not provide great girth strength. Thus the girth windings can commence as soon as the first layer formed of helical windings is completed and be laid between the first and second of these layers, or can, if needed, be applied in several layers between each of the helically wound layers. Contrariwise, several helically wound layers can be laid down before any girth winding was applied and then several further helically wound layers can be laid down before the next girth winding is commenced. In the construction of the present illustrative embodiment of the invention, however, a completed pattern of a girth winding extending from one end to the other of a cylindrical, body portion of a vessel is shown as applied between each complete helically wound pattern or layer. The layers so formed are represented in the FIG. 7 showing. by the reference characters 6 for the longitudinal helical one and 26 for the girth one. I

Another important aspect of the FIG. 7 showing is that as the girth windings terminate at the position 10 where the ovaloid end pattern departs from the cylindrical body portion at a tangent thereto, the thinnest part of the vessel wall commences. Actually this thinnest part is reached at the position 26 just outwardly from the position 10. The wall strength, however, at the position 26, for all requirements of the vessel, both internal pressure and external load is adequate due to the curvature and the close compacting of the helical windings. Obviously, the wall at the portion 27 bordering the end fitting is the thickest due to the crossing over of the windings at this position and the massing of them over the surface 12 of the end fitting where they all come tangent to the outer surface of the cylindrical portion 5 of that fitting.

The girth windings as shown are of no greater helix angle than that required to lay them side by side circumferentially of the body of the vessel. Also, the number of them is kept to the minimum for strength requirements, since the uses to which pressure vessels in accordance with the invention are put call for keeping down the weight as much as possible consonant with adequate strength.

Though the helical winding for the vessel of the invention has been shown as following a single cycle pattern, it is, of course, to be understood that this is merely for illustrative purposes. Patterns of two or more cycles, each commencing at circumferentially spaced positions, as more fully described in my application Serial Number 374,600, can be employed with equal facility.

Though the neck 5 of the end fitting has merely been shown with a plain opening therethrough, it is to be understood that this is merely for illustrative purposes and that any suitable thread or other engaging formation can be imparted to this opening if desired.

Insofar as the structure of the vessel is concerned, it has already been noted that besides being formed for resistance to internal pressure, vessels in accordance with the invention can be formed with end shapes generated to withstand axial external end loads.

As to possible shapes of vessels made in accordance with the invention they can vary from a long cylinder to a flattened sphere having no cylindrical joining portion. The latter when the vessel is made of flexible filaments or bands positioned by a flexible binder can serve as complete tire-like wheels for aircraft. Likewise flexible rollers can be made out of long cylindrical vessels.

In the event that a vessel is desired having an openwork pattern in the walls as shown in FIGS. 8, 9 and 10, such can be effected by varying the winding pattern, or patterns, to the desired extent. With regard to any small angle helical winding, instead of repeating a cycle in exact juxtaposed relation as shown at 15 and 20 in FIG. 3, the second and each subsequent cycle will be commenced with its winding in spaced relation to the commencement of the initial or next previous winding as the case may be. Winding in this manner will generate a series of crossovers leaving diamond shaped openings 23 in the vessel wall.

As the ends diminish toward the axis, the winding bands converge and the openings diminish and are eventually eliminated.

Should girth strengthening be desired this can be effected by the application of circular windings 25 around the body 9 passing through the crossover points. This converts the diamond shaped openings 28 into trianglar ones 29 and increases the rigidity of the structure as particularly shown in FIGS. 8 and 10.

From the foregoing description of the product and method of the invention it will be clear to those skilled in the art that the practice of the invention lends itself readily to various modifications whether suggested in the foregoing or not. that changes may be made in the disclosed method and modifications may be made in the structures and combinations of the same which embody the invention without departing from the scope of the invention. It is thus intended that all matter contained in the description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

This application is a division of application Serial No. 699,077, filed November 26, 1957, now Patent No. 3,047,191, granted July 31, 1962.

It is, accordingly, to be understood The invention claimed is:

1. A filament wound hollow vessel having a wall composed substantially of helical windings and including a body portion of generally cylindrical formation and ends extending tangentially from said body portion in a substantially ovaloid formation, part of the wall of said body portion being formed with substantially diamond shaped openings extending through the said wall and diminishing in size into said ends to form substantially closed ends.

2. A filament wound hollow vessel as in claim 1 and including substantially circular windings applied to said part of the wall of said body portion, said. windings bisecting said diamond shaped openings and converting them into triangular one extending through the said part of the wall of said body portion.

3. A filament wound hollow vessel formed with substantially closed ends, which comprises a pair of axially aligned ovaloid elements positioned with their enlarged ends in opposed relation and a cylindrical joining section extending between said enlarged ends of said ovaloid elements and joining the same together; the wall of said vessel, including said ovaloid elements, comprising a plurality of continuous filament helical windings extending substantially iongitudinally of said vessel at an angle substantially less than a right angle with respect to the axis thereof and continuing from one of said ovaloid elements to the other and back again; that part of said vessel wall which forms said cylindrical joining section together with a portion of each of said ovaloid end elements adjacent said cylindrical joining section containing substantially diamond-shaped openings extending through said part of said vessel wall and diminishing in size into the said ovaloid end elements to form substantially closed ends; the said diamond-shaped openings having been formed by commencing each said helical winding subsequent to the first of said windings, with its winding in spaced relation to the commencement of the preceding helical winding, and continuously maintaining said spaced relationship; said helical windings being bonded together with a suitable binder; and the curvature of the enlarged ends of said ovaloid elements being tangent to said cylindrical section where said ends and said cylindrical section are joined together.

4. A filament Wound vessel of claim 3, including substantially circular windings applied to the portion of said vessel wall forming said cylindrical joining section, each said circular winding bisecting a diamond-shaped opening to convert same into a triangular opening extending through said part of said vessel wall.

5. A filament wound hollow vessel having a wall composed substantially of helical windings and including a body portion of substantially identical ovaloid end formations having their area of maximum diameter centrally positioned, part of the wall of said body portion being formed with substantially diamond shaped openings extending through the said wall and diminishing in size into said end formations to form substantially closed ends.

6. A filament wound hollow vessel as in claim 5 and including substantially circular windings applied to said part of the wall of said body portion in the area of maximum diameter, said windings bisecting said diamond shaped openings and converting them into triangular ones extending through the said part of the wall of said body portion.

References Cited in the file of this patent UNITED STATES PATENTS 1,011,090 Subers Dec. 5, 1911 2,649,991 Woock Aug. 25, 1953 2,718,583 Noland et a1 Sept. 20, 1955 2,744,043 Ramberg May 1, 1956 FOREIGN PATENTS 775,577 Great Britain May 29, 1957 

1. A FILAMENT WOUND HOLLOW VESSEL HAVING A WALL COMPOSED SUBSTANTIALLY OF HELICAL WINDINGS AND INCLUDING A BODY PORTION OF GENERALLY CYLINDRICAL FORMATION AND ENDS EXTENDING TANGENTIALLY FROM SAID BODY PORTION IN A SUBSTANTIALLY OVALOID FORMATION, PART OF THE WALL OF SAID BODY PORTION BEING FORMED WITH SUBSTANTIALLY DIAMOND SHAPED OPENINGS EXTENDING THROUGH THE SAID WALL AND DIMINSHING IN SIZE INTO SAID ENDS TO FORM SUBSTANTIALLY CLOSED ENDS. 